1. Field of the Invention
This invention relates generally to ground proximity warning systems for aircraft, and more particularly to systems that monitor the altitude above ground and the closure rate of the aircraft to determine a hazardous flight condition. Even more particularly, the present invention relates to a system that warns the pilot of excessive terrain closure wherein the warning criteria are modified as a function of the descent rate of the aircraft to prevent warnings from being generated when the closure rate is the result of an intentional high descent rate such as that encountered during a dive or other abrupt maneuver.
2. Description of the Prior Art
Ground proximity warning systems that warn of a dangerous flight condition are known. Examples of such systems are disclosed in U.S. Pat. Nos. 3,934,221; 3,934,222; 3,944,968; 3,946,358 3,958,218 and 3,958,219 assigned to the assignee of the present invention. All of these systems monitor the radio altitude and the radio altitude closure rate and generate a warning if the rate of closure is excessive for the altitude at which the aircraft is flying.
While these systems do provide a way to warn a pilot of a hazardous condition resulting from an excessive closure rate with terrain, these systems are designed for use in transport aircraft, and not for highly maneuverable, high performance tactical aircraft such as the Lockheed S3-A whose flight and operational characteristics are such that high descent rates are often encountered in normal operation. Such high descent rates can result in sufficiently high closure rates to cause systems designed for transport aircraft to generate false or nuisance warnings during certain normal operational conditions of such an aircraft.